A known switching valve for the same general purpose as that of the present invention is shown in German Offenlegungsschrift No. 22 41 883, in which two valve bodies are configured as oppositely rotatable rotary slide valves. A space exists between those bodies, permitting troublesome leakage losses especially when measuring the pressure of fluid which is of low viscosity.
A solution to this leakage problem is proposed in German OS No. 27 52 575 which shows a plurality of valve seats, corresponding in number to the measuring points, on a rotary slide valve, the valve members for which must be moved each time out of their closed positions against the force of a spring which requires the use of considerable force.
It is also known, when using ball cocks, to use packing bodies with annular packing surfaces. These packing bodies and packing surfaces are of a very rugged nature and no notice need be taken of them here, whether their annular packing surfaces are pressed more or less strongly against the spherical zone.